Steel structure plants are primarily defined by their main load-bearing components, which are composed of robust steel, including steel columns, beams, foundations, and roof trusses. Modern steel roofs often span large distances, and walls may be made from either steel structures or maintained by brick walls. With the growth of China's steel production, steel structure plants have become prevalent, further categorized into light and heavy steel structures. Industrial and civil facilities constructed of steel are known as steel structures. Key features of steel structure plants include: 1. Lightweight buildings with high strength and large spans. 2. Shorter construction periods, leading to reduced investment costs. 3. High fire resistance and strong corrosion resistance. 4. Easy relocation and recycling, making them environmentally friendly.
Advanced Construction Technology for Steel Structures
Scope of Application: This technology is ideal for the comprehensive processing of building steel structures, encompassing process flow selection, lofting, marking, cutting, correction, molding, edge processing, tube ball processing, hole making, friction surface processing, end processing, component assembly, round tube component processing, and pre-assembly of steel components.
1. Material Requirements
1.1.1 All steel, welding materials, coating materials, and fasteners must come with quality certifications, meeting both the design requirements and current industry standards.
1.1.2 Incoming raw materials must not only have manufacturer quality certificates but also undergo on-site sampling, testing, and acceptance under the supervision of Party A and the relevant authorities, according to contract terms and current standards. Inspection records and reports should be provided to Party A and the supervisory team.
1.1.3 If any defects in raw materials are identified during processing, they must be evaluated and handled by inspectors and qualified technicians.
1.1.4 Any material substitution requests must be submitted in advance by the manufacturing unit, including an application form (technical approval sheet) and material certificate, to be approved by Party A, the supervisor, and confirmed by the design unit.
1.1.5 The use of electrodes with peeling or rusted cores, damp caked or melted flux, and rusty wires is strictly prohibited. Studs used for welding must be free from defects such as cracks, striations, dents, and burrs.
1.1.6 Welding materials should be centrally managed in a dedicated, dry, and well-ventilated warehouse.
1.1.7 Bolts must be stored in a dry and ventilated room. High-strength bolt acceptance should follow the national standard 'Design, Construction, and Acceptance Procedures for High-Strength Bolt Connections in Steel Structures' JGJ82. Corroded, stained, damp, bruised, or mixed batch high-strength bolts are strictly prohibited.
1.1.8 Paint must meet design specifications and be stored in a dedicated warehouse. Expired, deteriorated, caked, or ineffective paint is strictly prohibited.
2. Main Machinery
Steel Structure
Hai Luo Steel Structure
1.2.1 Main Equipment
Long Tools for Steel Structure Production.
3. Operating Conditions
1.3.1 Detailed construction drawings must be completed and approved by the original designer.
1.3.2 All technical preparations, including construction organization design, construction schemes, and operation instructions, must be completed.
1.3.3 Various process evaluation tests, process performance tests, and material purchase plans must be completed.
1.3.4 All main materials must have arrived at the factory.
1.3.5 Comprehensive debugging and acceptance of various mechanical equipment to ensure optimal performance and reliability.
1.3.6 Our production team has undergone rigorous pre-construction training and holds the necessary qualification certificates, ensuring top-notch expertise.
4 Operation process
1.4.1 Process flow
1.4.2 Operation process
1 Lofting, marking material
1) Thorough examination of construction drawings; any issues identified should be promptly addressed with the relevant technical departments.
2) Prepare sample materials such as thin iron sheets and flat steel for testing and demonstration purposes.
3) Ensure that the steel ruler used in lofting is verified and approved by the metrological department for accuracy.
4) Familiarize with the material specifications and quality before quantifying materials. Different specifications and parts should be categorized accordingly, adhering to the principle of prioritizing larger parts first.
5) Clearly mark sample rods with processing numbers, component details, and specifications. Indicate critical processing symbols such as hole diameters and bending lines.
6) Consider shrinkage and machining allowance during lofting and marking, including allowances for on-site welding shrinkage and cutting/milling processes.
Milling end allowance: generally add 3-4mm per side post-cutting and 4-5mm per side post-gas cutting.
Cutting margin: automatic gas cutting slit width is 3mm, while manual gas cutting slit width is 4mm.
Welding shrinkage allowance is determined based on the structural characteristics of the component.
7) For main force members and those requiring bends, ensure material direction compliance and avoid impact points or scars on the exterior of bent parts.
8) Marking should facilitate cutting and ensure high-quality parts production.
9) Residual materials post-marking should be clearly identified by number, specification, material, and batch number for efficient reuse.
2 Cutting
Post-blanking, steel must be cut precisely according to the specified shape and size.
1) Key considerations during cutting:
(1) Pre-arrange a reasonable cutting sequence when multiple parts are laid out on a steel plate with intersecting shear lines.
(2) Correct any bending deformation post-shearing; trim and polish rough or burred shear surfaces.
(3) During shearing, ensure important structural parts and weld interfaces are processed via milling, planing, or grinding wheel to accommodate metal deformation.
2) For sawing operations, consider the following:
(1) Ensure section steel is straightened before sawing.
(2) For single-piece sawing, draw a marking line first, then cut. Batch-processed components should utilize positioning baffles for precision.
(3) For components requiring high machining accuracy, reserve appropriate allowances for face finishing post-sawing.
(4) Maintain control over the perpendicularity of the cutting section during sawing.
3) Key process points for gas cutting operations:
(1) Prior to commencing gas cutting, it is imperative to meticulously inspect all equipment and tools within the gas cutting system to guarantee their optimal operational status and ensure utmost safety.
(2) Carefully select the appropriate process parameters for gas cutting. During the cutting process, adjust the oxygen jet (wind line) to maintain a defined outline, achieve a prolonged wind line, and ensure robust shooting force.
(3) Pre-gas cutting preparation involves the removal of dirt, oil, floating rust, and other surface debris from the steel. Additionally, ensure there is adequate clearance beneath to facilitate efficient slag removal.
(4) Vigilantly guard against tempering during the gas cutting process to prevent any unintended consequences.
(5) To mitigate deformation during gas cutting, initiate cuts from the shorter side. Prioritize cutting smaller parts before larger ones and tackle more complex shapes prior to simpler ones.
3 Correction and Forming
1) Correction
(1) Conduct cold correction on finished products using mechanical tools such as flange levelers, straighteners, hydraulic presses, and other similar equipment.
(2) For flame correction, utilize heating techniques like point heating, linear heating, and triangular heating.
The optimal thermal correction temperature for low carbon steel and standard low alloy steel ranges between 600°C and 900°C. The ideal temperature for thermoplastic deformation is 800°C to 900°C, with a strict upper limit of 900°C.
Medium carbon steel is prone to cracking under deformation, thus flame correction is generally avoided for this material.
Ordinary low-alloy steel should undergo gradual cooling post-heating correction to ensure structural integrity.
Process Flow
2) Forming
(1) Hot processing of low carbon steel typically occurs at temperatures between 1000°C to 1100°C, with the processing termination temperature not falling below 700°C. The heating temperature should be around 500°C to 550°C. Steel becomes brittle at these temperatures, so hammering and bending are strictly prohibited to avoid breakage.
(2) Cold processing involves working the steel at room temperature, primarily utilizing specialized mechanical equipment and tools.
4 Edge Machining (Including End Milling)
1) Common edge processing methods include cutting, planing, milling, carbon arc gouging, gas cutting, and bevel machining.
2) For gas-cut parts requiring edge processing to eliminate the affected zone, a minimum processing allowance of 2.0mm must be maintained.
3) The edge machining depth must ensure the complete removal of surface defects, maintaining a minimum depth of 2.0mm. Post-processing, the surface must remain undamaged and crack-free, with grinding traces aligning with the edge when using a grinding wheel.
4) Manually cut edges of carbon structural steel parts must be cleaned thoroughly, ensuring no roughness exceeds 1.0mm.
5) The supporting side at the end of the member requires a precisely planed top and high section accuracy. Regardless of cutting method or steel type, planing or milling is essential.
6) For construction drawings with specific welding requirements, edges must be planed. However, shear edges of general plates or steel typically do not require planing.
7) Post mechanical automatic cutting and air arc cutting, the edge flatness must not exceed 1.0mm. The free edge of the main stress member requires a post-gas cutting processing allowance of at least 2mm per side, free from burrs and other defects.
8) After the column end milling, ensure that at least 75% of the top contact surface fits snugly within a 0.3mm tolerance. The stuffing area should not exceed 25%, and the edge gap should be no greater than 0.5mm for optimal performance.
9) The selection of milling parameters, such as milling speed and depth, should be based on the material of the workpiece and specific processing requirements. This careful selection is crucial for maintaining high processing quality.
10) Component end processing must be performed only after the correction process has been thoroughly verified and deemed accurate.
11) Appropriate measures should be taken based on the component's form to ensure that the milling end remains perfectly perpendicular to the axis, ensuring precision and quality.
Five-hole system
1) The manufacture of high-strength bolts, including large hexagonal head bolts, torsional shear bolts, semi-round head rivet self-tapping screws, and other hole types can be achieved through various methods such as drilling, milling, punching, reaming, or countersinking.
2) Drilling is the preferred method for component hole creation. Punching is permissible only if it can be demonstrated that the material's quality, thickness, and aperture will not suffer brittleness post-punching.
All ordinary structural steels with a thickness of less than 5mm may be punched. Minor structures with a thickness under 12mm can also be punched. Post-punching welding is not allowable unless it can be proven that the material retains significant toughness. When drilling larger holes to be punched, ensure the hole is 3mm smaller than the specified diameter.
3) Prior to drilling, it is essential to grind the drill bit and to select an appropriate chip allowance for efficient drilling operations.
4) Bolt holes must be cylindrical and perpendicular to the steel surface at the drilling location. The inclination should be less than 1/20, and the hole perimeter should be free of burrs, cracks, flares, or bumps. Clear any cutting debris immediately.
5) For refined or reamed bolt holes, the diameter should match the bolt rod. Achieve H12 precision after drilling or assembly, and ensure the surface roughness of the hole wall is less than 12.5μm.
6 Friction surface processing
1) High-strength bolted friction surfaces can be treated using sandblasting, shot blasting, or grinding. Ensure the grinder's direction is perpendicular to the force direction of the component, and the grinding range is at least 4 times the bolt diameter.
2) After treatment, friction surfaces must be protected from oil and other damages to maintain their integrity.
3) Both the manufacturer and installation unit should conduct anti-slip coefficient tests on steel structure manufacturing batches. For batches up to 2000t, divide into divisions (sub-parts). When multiple surface treatment processes are used, inspect each process separately with three groups of specimens per batch.
4) Specimens for anti-slip coefficient tests must be processed by the manufacturer. Ensure that they and the steel structural members they represent are made of the same material, in the same batch, with identical friction surface treatment and state, and the same high-strength bolt connection pairs under consistent environmental conditions.
5) The thickness of the specimen steel plate should reflect the representative thickness of the steel structure engineering. The plate surface must be smooth and oil-free, with no flash or burr at the hole edges.
6) The manufacturer should conduct anti-slip coefficient tests during steel structure production and issue a report detailing the test methods and results for transparency and quality assurance.
7) Components with the same material and treatment method for retesting anti-slip coefficient should be manufactured following the guidelines of the current national standard "Design, Construction, and Acceptance Procedures for High-Strength Bolted Connection of Steel Structures" JGJ82 or the design document provisions. These components should be submitted simultaneously.
7) Tube ball processing
1) Rod production process: procure steel pipe → inspect material, specifications, surface quality (anti-corrosion treatment) → cutting, beveling → spot welding with cone head or seal plate assembly → welding → inspection → pre-anti-corrosion treatment → anti-corrosion treatment.
2) Bolt ball manufacturing process: steel bar (or ingot) for pressure processing or round steel for machining → forging blank → normalizing treatment → processing positioning thread hole (M20) and its surface → processing each thread hole and plane → applying worker number and ball number → anti-corrosion pretreatment → anti-corrosion treatment.
3) Cone head and sealing plate production process: finished steel blanking → die forging → normalizing → mechanical processing.
4) Welding ball joint grid manufacturing process: procure steel pipe → inspect material, specifications, surface quality → lofting → cutting → hollow ball production → assembly → anti-corrosion treatment.
5) Welding hollow ball production process: blanking (with copying cutter) → pressing (heating) molding → machine tool or automatic gas cutting groove → welding → weld non-destructive inspection → anti-corrosion treatment → packaging.
8) Assembly
1) Before assembly, staff must be familiar with the construction drawings and related technical requirements of the components, and review part quality according to construction drawings.
2) Due to insufficient raw material size or technical requirements, parts generally must be spliced before assembly.
3) The following requirements must be followed for mold assembly:
(1) The selected site must be smooth and have sufficient strength.
(2) When arranging the assembly mold, consider prerelease welding shrinkage and other processing allowances according to steel structure characteristics.
(3) After assembling the first batch of components, they must be comprehensively inspected by the quality inspection department. Assembly can continue after passing inspection.
(4) Components must be assembled in strict accordance with process regulations. Hidden welds must be welded first and covered after inspection. For complex parts that are difficult to weld, use the method of welding while assembling.
(5) To reduce deformation and assembly sequence, first assemble into components, then assemble components together.
4) Select the assembly method for steel structure components based on structural characteristics, technical requirements, manufacturer processing capacity, mechanical equipment, etc., to effectively control assembly quality and ensure high production efficiency.
5) Typical structure assembly
(1) Welding H-beam construction technology
Process flow
Cutting → assembly → welding → correction → secondary cutting → hole making → welding other parts → correction and grinding
(2) Processing technology of box section components
(3) Processing technology of the rigid cross column
(4) General pipe rolling process flow chart
1) The number of pre-assemblies shall be according to design requirements and technical documents.
2) The selection principle of pre-assembly components: Prioritize those with a primary stress framework, intricate joint connections, and components with tolerance limits nearing the extreme. These should be representative of composite components.
3) Pre-assembly must be conducted on a robust and stable platform tire frame. Ensure its bearing point levelness:
A≤300 ~ 1000m² with a tolerance of ≤2mm
A≤1000 to 5000m² with an unspecified tolerance< 3mm
(1) During pre-assembly, all components should adhere strictly to construction drawings. The center of gravity lines for each section must converge precisely at the node's center and remain completely free, without any external forces fixing them. Each single member, whether column, beam, or support, should be supported at no fewer than two points.
(2) Pre-assembled components must have clearly marked center lines that align with the platform and ground baselines. These control bases should conform to design requirements. Any changes to the pre-assembly basis position must be approved by the process design team.
(3) All components requiring pre-assembly must be individual components approved by special inspectors, meeting stringent quality standards post-production. Identical single members should be interchangeable without compromising the overall geometry.
(4) Throughout the pre-assembly process on the tire frame, components must not be altered or cut using flames or machinery. The use of heavy weights for ballast, colliding, or hammering is strictly prohibited.
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